For half a century, Ernst B. Haas was an extraordinarily prolific contributor to theoretical debates in international relations. His work focused on the question of continuity and transformation in the system of states. His substantive writings are extremely diverse and can be difficult, so no overall appreciation has ever been attempted. This essay pulls together the major strands of Haas' theoretical work into a coherent whole and seeks to make it accessible to the broadest possible audience of IR scholars. The first section locates Haas in the overall theoretical milieu in which his thinking evolved, and it identifies some core intellectual choices he made. The next three sections summarize Haas' main theoretical contributions to the fields of European integration, the study of change at the level of the world polity, and nationalism.

Subject:
international transformation; European integration; global governance; nationalism; constructivism in international relations theory